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Iontronics exploits mobile ions within electrolytes to control the electronic properties of materials and devices' electrical and optical response. In this frame, ionic liquids are widely exploited for the gating of semiconducting nanostructure devices, offering superior performance compared to conventional dielectric gating. In this work, we engineer ionic liquid gated InAs nanowire-based field effect transistors and adopt the set-and-freeze dual gate device operation to probe the nanowires in several ionic gate regimes. We exploit standard back-gating at 150 K, when the ionic liquid is frozen and any crosstalk between the ionic gate and the back gate is ruled out. We demonstrate that the liquid gate polarization has a persistent effect on the nanowire properties. This effect can be conveniently exploited to fine-tune the properties of the nanowires and enable new device functionalities. Specifically, we correlate the modification of the ionic environment around the nanowire to the transistor threshold voltage and hysteresis, on/off ratio and current level retention times. Based on this, we demonstrate memory operations of the nanowire field effect transistors. Our work shines a new light on the interaction between electrolytes and semiconducting nanostructures, providing useful insights for future applications of nanodevice iontronics.

We report an experimental study of a 1D quintuple-quantum-dot array integrated with two charge sensors in an InAs nanowire. The device is studied by measuring double quantum dots formed consecutively in the array, and corresponding charge stability diagrams are revealed with both direct current measurements and charge sensor signals. The one-dimensional quintuple-quantum-dot array is then tuned up, and its charge configurations are fully mapped out with the two charge sensors. The energy level of each dot in the array can be controlled individually using virtual gates. After that, four dots in the array are selected to form two double quantum dots, and ultrastrong inter-double-dot interaction is obtained. A theoretical simulation confirms the strong coupling strength between the two double quantum dots. The highly controllable one-dimensional quantum dot array is expected to be valuable for employing InAs nanowires to construct advanced quantum hardware in the future.

Strict requirements for target detection and identification of the complex background have increased because a single detection method is susceptible to environmental factors. The abilities to use terahertz imaging systems with high photoresponsivity and polarization sensitivity are of central importance to practical photodetectors. The present technology for high‐sensitivity, polarization THz detectors integrated into a compact, common aperture (co‐aperture) system remains largely unexplored challenges. By exploiting the inherent features of graphene/Bi2Te3 Dirac material and InAs nanowire, the plasma‐wave and thermoelectric co‐aperture phototransistors with a selective, synchronous, and controllable operating modes are devised in the same field of view, which provide remarkable efficiencies for THz‐light harvesting on‐chip. The achieved selective detection, better than that of single nanowire phototransistor, exhibits excellent sensitivity of 18.5 mA W−1 (12 V W−1) in graphene/Bi2Te3 channel and 3.5 mA W−1 (400 V W−1) in InAs nanowire channel, corresponding to the noise equivalent power of less than 0.1 nW/Hz0.5. The results are exploited to highlight a novel strategy for the realization of efficient co‐aperture phototransistors toward tunable, multiple modes, polarization THz detection by combining with in situ integration advantages of various materials, compatibility mechanisms, integration structures with metamaterials. [ABSTRACT FROM AUTHOR]

In this paper, an artificial nanoscale optoelectronic synapse is designed and simulated. The device is based on an InAs nanowire phototransistor covered with a native oxide layer, which captures the photo-generated hot electrons before the thermalization back to the conduction band. Due to the large surface-to-volume ratio and high electron mobility of InAs nanowire, the device exhibits a high responsivity of 104 A/W under 633 nm excitation at 300 K. At low illumination power density range of 10–5 ~ 3 W/cm2, the device shows synaptic behaviors including short-term potentiation, long-term potentiation and paired-pulse facilitation. The influence of different factors, including illumination intensity, gate voltage and the depth and concentration of traps on the synaptic behaviors, is studied in detail. By adjusting the gate voltage, a transition from short-term potentiation to long term potentiation is realized. The synaptic behaviors are explained by energy band diagram and distribution of current density and trapped charges. This work may pave the way for the development of low-consumption high-speed large-bandwidth synaptic devices. [ABSTRACT FROM AUTHOR]

Theoretical calculations are performed on lattice thermal conductivity (LTC) and related parameters for the zinc blende and wurtzite structure of InAs nanowires (NWs) with diameters of 50, 63, 66, 100 and 148 nm through the Morelli–Callaway model. For the model to be efficiently applicable, the longitudinal and transverse modes are considered. The melting point of the various-sized NWs is considered to estimate the Debye and phonon group velocities. The impacts of Grüneisen parameter, dislocations and surface roughness are also successfully utilized to address the calculated and measured LTC of the semiconductor under investigation. Results show that the Grüneisen parameter increases with decreasing NW diameter and that phonon confinement leads to an observable deviation of the calculated LTC curve from that of the experimental one in the case of bulk InAs. We assume that NW boundaries, dislocations and imperfections are responsible for the scattering of phonons along with electrons and other phonons because of normal and Umklapp processes. Therefore, at a specified temperature, LTC depends on the size and crystal structure of the semiconductor. As such, the thermal and mechanical parameters of InAs can be greatly modified by decreasing the size and dimension of the semiconductor as a result of the quantum-confinement effect. [ABSTRACT FROM AUTHOR]

Core-only InAs nanowires (NWs) remain of continuing interest for application in modern optical and electrical devices. In this paper, we utilize the II-VI semiconductor CdSe as a shell for III-V InAs NWs to protect the electron transport channel in the InAs core from surface effects. This unique material configuration offers both a small lattice mismatch between InAs and CdSe and a pronounced electronic confinement in the core with type-I band alignment at the interface between both materials. Under optimized growth conditions, a smooth interface between the core and shell is obtained. Atom probe tomography (APT) measurements confirm substantial diffusion of In into the shell, forming a remote n-type doping of CdSe. Moreover, field-effect transistors (FETs) are fabricated, and the electron transport characteristics in these devices is investigated. Finally, band structure simulations are performed and confirm the presence of an electron transport channel in the InAs core that, at higher gate voltages, extends into the CdSe shell region. These results provide a promising basis toward the application of hybrid III-V/II-VI core/shell nanowires in modern electronics.

The thermal conduction by the difference in the substrate of InAs nanowires (NWs) was investigated by determining the local temperature using Raman spectroscopy as an optical method. The optoelectric characteristics of the supported and suspended InAs nanowires were also investigated. The change in the current with the laser power produced a characteristic profile depending on the InAs nanowire configuration. The persistent photoconductivity (PPC) effect in the InAs nanowires has not been previously studied in detail despite its importance for the material photoresponse. This report presents a study of the PPC effect and the underlying mechanism. The correlation between the PPC effect and the thermal conduction by the substrate-induced carrier redistribution in the InAs nanowires is highlighted. In addition, a unique PPC effect associated with a specific device structure is studied. Our results can enable novel functionalities for InAs-based optoelectric applications in the future. [ABSTRACT FROM AUTHOR]

We report the occurrence of the zero-bias conductance peak (ZBCP) in an InAs nanowire coupled to PbIn superconductors with varying temperature, bias voltage, and magnetic field. The ZBCP is suppressed with increasing temperature and bias voltage above the Thouless energy of the nanowire. Applying a magnetic field also diminishes the ZBCP when the resultant magnetic flux reaches the magnetic flux quantum h /2 e . Our observations are consistent with theoretical expectations of reflectionless tunneling, in which the phase coherence between an electron and its Andreev-reflected hole induces the ZBCP as long as time-reversal symmetry is preserved. [ABSTRACT FROM AUTHOR]

Abstract: Negative photoconductivity (NPC) mechanisms are widely investigated for high‐performance InAs nanowire (NW) phototransistors, where these mechanisms are usually attributed to severe carrier scattering centers, light‐assisted hot electron trapping in the surface oxide, and/or defects induced photogating layer. However, further insights into their photodetecting mechanisms, as well as corresponding performance enhancement of these NW phototransistors, are still very limited. This work reports the NPC behavior in surface‐modified InAs NW phototransistors based on photoexcitation induced majority electron trapping in the bonded sulfur monolayer under optical illumination. In order to enhance hot electron trapping ability of the bonded sulfur layer, aromatic thiolate (ArS−)‐based molecular monolayer with strong electron‐withdrawing group is employed using simple wet chemistry for the surface modification of InAs NW phototransistors. The magnitude of the photoexcitation induced hot electron trapping is increased by the stronger electron‐withdrawing ability of the ArS−‐based molecular monolayer, enabling the hot electrons to be trapped and released more efficiently, resulting in NW phototransistors with good sensitivity, fast photoresponse, and long‐term stability to low intensity visible light. These results confirm the potential of InAs NW phototransistors surface‐passivated with molecular monolayers in the application and realization of high‐sensitive and long‐term stable room temperature nanoscale photodetectors. [ABSTRACT FROM AUTHOR]

We demonstrate an original method based on controlled oxidation for creating high-quality tunnel junctions between superconducting Al reservoirs and InAs semiconductor nanowires (NWs). We show clean tunnel characteristics with a current suppression by >4 orders of magnitude for a junction bias well below the Al gap of Δ ≈ 200 μeV. The experimental data agree well with the Bardeen-Cooper-Schrieffer theoretical expectations for a superconducting tunnel junction. The studied devices employ small-scale tunnel contacts functioning as thermometers as well as larger electrodes that provide proof-of-principle active cooling of the electron distribution in the NWs. A peak refrigeration of approximately δ T = 10 mK is achieved at a bath temperature of T ≈ 250-350 mK for our prototype devices. This method introduces important perspectives for the investigation of the thermoelectric effects in semiconductor nanostructures and for nanoscale refrigeration. [ABSTRACT FROM AUTHOR]

A highly tunable linear triple quantum dot (TQD) device is realized in a single-crystalline pure-phase InAs nanowire using a local finger gate technique. The electrical measurements show that the charge stability diagram of the TQD can be represented by three kinds of current lines of different slopes and a simulation performed based on a capacitance matrix model confirms the experiment. We show that each current line observable in the charge stability diagram is associated with a case where a QD is on resonance with the Fermi level of the source and drain reservoirs. At a triple point where two current lines of different slopes move together but show anticrossing, two QDs are on resonance with the Fermi level of the reservoirs. We demonstrate that an energetically degenerated quadruple point at which all three QDs are on resonance with the Fermi level of the reservoirs can be built by moving two separated triple points together via sophistically tuning of energy levels in the three QDs. We also demonstrate the achievement of direct coherent electron transfer between the two remote QDs in the TQD, realizing a long-distance coherent quantum bus operation. Such a long-distance coherent coupling could be used to investigate coherent spin teleportation and superexchange effects and to construct a spin qubit with an improved long coherent time and with spin state detection solely by sensing the charge states. [ABSTRACT FROM AUTHOR]

III-V compound semiconductors are indispensable materials for today's high-end electronic and optoelectronic devices and are being explored for next-generation transistor logic and quantum technologies. III-V surfaces and interfaces play the leading role in determining device performance, and therefore, methods to control their electronic properties have been developed. Typically, surface passivation studies demonstrated how to limit the density of surface states. Strain has been widely used to improve the electronic transport properties and optoelectronic properties of III-Vs, but the potential of this technology to modify the surface properties still remains to be explored. Here we show that uniaxial stress induces a shift in the energy of the surface states of III-V nanowires, modifying their electronic properties. We demonstrate this phenomenon by modulating the conductivity of InAs nanowires over 4 orders of magnitude with axial strain ranging between -2.5% in compression and 2.1% in tension. The band bending at the surface of the nanostructure is modified from accumulation to depletion reversibly and reproducibly. We provide evidence of this physical effect using a combination of electrical transport measurement, Raman spectroscopy, band-structure modeling, and technology computer aided design (TCAD) simulations. With this methodology, the deformation potentials for the surface states are quantified. These results reveal that strain technology can be used to shift surface states away from energy ranges in which device performance is negatively affected and represent a novel route to engineer the electronic properties of III-V devices. [ABSTRACT FROM AUTHOR]

We report on a prototype device geometry where a number of quantum point contacts are connected in series in a single quasi-ballistic InAs nanowire. At finite magnetic field the backscattering length is increased up to the micron-scale and the quantum point contacts are connected adiabatically. Hence, several input gates can control the outcome of a ballistic logic operation. The absence of backscattering is explained in terms of selective population of spatially separated edge channels. Evidence is provided by regular Aharonov-Bohm-type conductance oscillations in transverse magnetic fields, in agreement with magnetoconductance calculations. The observation of the Shubnikov-de Haas effect at large magnetic fields corroborates the existence of spatially separated edge channels and provides a new means for nanowire characterization. [ABSTRACT FROM AUTHOR]

One-dimensional ballistic transport is demonstrated for a high-mobility InAs nanowire device. Unlike conventional quantum point contacts (QPCs) created in a two-dimensional electron gas, the nanowire QPCs represent one-dimensional constrictions formed inside a quasi-one-dimensional conductor. For each QPC, the local subband occupation can be controlled individually between zero and up to six degenerate modes. At large out-of-plane magnetic fields Landau quantization and Zeeman splitting emerge and comprehensive voltage bias spectroscopy is performed. Confinement-induced quenching of the orbital motion gives rise to significantly modified subband-dependent Landé g factors. A pronounced g factor enhancement related to Coulomb exchange interaction is reported. Many-body effects of that kind also manifest in the observation of the 0.7·2e2/h conductance anomaly, commonly found in planar devices. [ABSTRACT FROM AUTHOR]

We demonstrate the growth and structural characteristics of InAs nanowire junctions evidencing a transformation of the crystalline structure. The junctions are obtained without the use of catalyst particles. Morphological investigations of the junctions reveal three structures having an L-, T-, and X-shape. The formation mechanisms of these structures have been identified. The NW junctions reveal large sections of zinc blende crystal structure free of extended defects, despite the high stacking fault density obtained in individual InAs nanowires. This segment of zinc blende crystal structure in the junction is associated with a crystal phase transformation involving sets of Shockley partial dislocations; the transformation takes place solely in the crystal phase. A model is developed to demonstrate that only the zinc blende phase with the same orientation as the substrate can result in monocrystalline junctions. The suitability of the junctions to be used in nanoelectronic devices is confirmed by room-temperature electrical experiments. [ABSTRACT FROM AUTHOR]

The electrochemical lithiation/delithiation processes of InAs nanowires (NWs) are studied by in-situ transmission electron microscopy. Our results indicate that InAs NWs have a fast lithiation speed of 275 nm/s and a high lithium ion (Li-ion) diffusion coefficient of 2.49×10 −8 cm 2 /s at room temperature. Upon lithiation, the Li-ion insertion firstly results in severe lattice distortions of InAs NWs, and the formation of Li 3 As and Li x In through the conversion and alloying processes take place on further lithiation. A small volume expansion of 157% is observed in full lithiation and is attributed to the naturally formed surface oxide layer. During the delithiation process, volume contraction and the dealloying of Li x In take place. Induced by the alloying and dealloying of Li x In, the dark and bright strips along the basal plane of InAs NWs appear and disappear alternately during the lithiation–delithiation cycling. Our results provide important insights into the lithiation/delithiation mechanism of III–V group nanomaterials and are envisaged to be helpful for designing lithium ion battery anode materials with fast lithiation speed, small volume expansion and reversible lithiation/delithiation processes. [ABSTRACT FROM AUTHOR]

We constructed the Hamiltonian of spin–orbit splitting for carriers of a tubular electron gas in InAs nanowires. The spectral problem is solved using an exact numerical diagonalization. It is shown that the contribution of k -linear Dresselhaus-like spin–orbit (SO) coupling leads to renormalization of the so-called SO-gaps and appearance of anticrossings in subband spectrum. These features can be detected in ballistic transport. [ABSTRACT FROM AUTHOR]

Through studying the transfer curve of field effect transistors (FETs) and the current response at various gate voltages, we observe that the adsorption of H 2 O vapor and NO 2 introduce opposite effect to the performance of InAs nanowire (NW) FETs compared with that in the vacuum. Although the hysteresis in the transfer curve increases in both the gases, the threshold voltage shifts negatively in H 2 O vapor and positively in NO 2 /N 2 gas due to the different response mechanisms. The transconductance and the field-effect mobility of the devices do not change in H 2 O for both the gate voltage sweeping directions and in NO 2 /N 2 for forward sweeping compared with that in the vacuum, probably due to the InO x layer covering the InAs NW. Importantly, current response to H 2 O and NO 2 can be modulated by the gate voltage. Analysis suggests that the effect of H 2 O adsorption is to increase electron density, while the effect of NO 2 adsorption is to decrease the electron density in the channel. [ABSTRACT FROM AUTHOR]

InAs is a direct, narrow band gap (0.354 eV) material with ultrahigh electron mobility, and is potentially a good optoelectronic device candidate in the wide UV-visible-near-infrared region. In this work we report the fabrication of InAs nanowire-based photodetectors, which showed a very high photoresponse over a broad spectral range from 300 to 1,100 nm. The responsivity, external quantum efficiency and detectivity of the device were respectively measured to be 4.4 × 10 3 AW −1, 1.03 × 10 6%, and 2.6 × 10 11 Jones to visible incident light. Time dependent measurements at different wavelengths and under different light intensities also demonstrated the fast, reversible, and stable photoresponse of our device. Theoretical calculations of the optical absorption and the electric field component distribution were also performed to elucidate the mechanism of the enhanced photoresponse. Our results demonstrate that the single-crystalline InAs NWs are very promising candidates for the design of high sensitivity and high stability nanoscale photodetectors with a broad band photoresponse. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

To clarify the ultrafast temporal interplay of the different photocurrent mechanisms occurring in single InAs-nanowire-based circuits, an on-chip photocurrent pump-probe spectroscopy based on coplanar striplines was utilized. The data are interpreted in terms of a photo-thermoelectric current and the transport of photogenerated holes to the electrodes as the dominating ultrafast photocurrent contributions. Moreover, it is shown that THz radiation is generated in the optically excited InAs-nanowires, which is interpreted in terms of a dominating photo-Dember effect. The results are relevant for nanowire-based optoelectronic and photovoltaic applications as well as for the design of nanowire-based THz sources. [ABSTRACT FROM AUTHOR]

We propose and demonstrate experimentally a novel configuration for observing spin interference effects in the conductance of quantum rings. Our configuration, in which the conducting ring and the tangential current lead form a single collimating contact, precludes spin rotation in the contact region. We have observed the spin quantum beating in the Aharonov–Bohm (AB) conductance oscillations. This beating is the result of a superposition of two independent interference signals associated with the intrinsic spin–orbit interactions. Our work provides conclusive evidence of the spin Berry phase in the ring conductance. [Copyright &y& Elsevier]

Thermoelectric measurements have the potential to uncover the density of states (DOSs) of low-dimensional materials. Here, we present the anomalous thermoelectric behavior of monolayer graphene-nanowire (NW) heterostructures, showing large oscillations as a function of the doping concentration. Our devices consist of InAs NW and graphene vertical heterostructures, which are electrically isolated by thin (∼10 nm) hexagonal boron nitride (hBN) layers. In contrast to conventional thermoelectric measurements, where a heater is placed on one side of a sample, we use the InAs NW (diameter ∼50 nm) as a local heater placed in the middle of the graphene channel. We measure the thermoelectric voltage induced in graphene due to Joule heating in the NW as a function of temperature (1.5-50 K) and carrier concentration. The thermoelectric voltage in bilayer graphene (BLG)-NW heterostructures shows sign change around the Dirac point, as predicted by Mott's formula. In contrast, the thermoelectric voltage measured across monolayer graphene (MLG)-NW heterostructures shows anomalous large-amplitude oscillations around the Dirac point, not seen in the Mott response derived from the electrical conductivity measured on the same device. The anomalous oscillations are a signature of the modified DOSs in MLG by the electrostatic potential of the NW, which is much weaker in the NW-BLG devices. Thermal calculations of the heterostructure stack show that the temperature gradient is dominant in the graphene region underneath the NW, and thus sensitive to the modified DOSs resulting in anomalous oscillations in the thermoelectric voltage. Furthermore, with the application of a magnetic field, we detect modifications in the DOSs due to the formation of Landau levels in both MLG and BLG., (© 2021 IOP Publishing Ltd.)

We study the magnetotransport properties of single InAs nanowires grown by selective-area metal-organic vapor-phase epitaxy. The semiconducting InAs nanowires exhibit a large positive ordinary magnetoresistance effect. However, a deviation from the corresponding quadratic behavior is observed for an orientation of the applied magnetic field perpendicular to the nanowire axis. This additional contribution to the magnetoresistance can be explained by diffuse boundary scattering of free carriers in the InAs nanowire and results in a reduction of the charge carrier mobility. As a consequence, angle-dependent magnetotransport measurements reveal a highly anomalous behavior. Numerical simulations have been conducted to further investigate the effect of classical boundary scattering in the nanowires. On the basis of the numerical simulations, an empirical description is derived, which yields excellent agreement with the experimental data and allows one to quantify the contribution of boundary scattering to the magnetoresistance effect.

We report on experimental detection of the spin-orbit interaction field in an InAs nanowire double quantum dot device. In the spin blockade regime, leakage current through the double quantum dot is measured and is used to extract the effects of spin-orbit interaction and hyperfine interaction on spin state mixing. At finite magnetic fields, the leakage current arising from the hyperfine interaction can be suppressed, and the spin-orbit interaction dominates spin state mixing. We observe dependence of the leakage current on the applied magnetic field direction and determine the direction of the spin-orbit interaction field. We show that the spin-orbit field lies in a direction perpendicular to the nanowire axis but with a pronounced off-substrate-plane angle. The results are expected to have an important implication in employing InAs nanowires to construct spin-orbit qubits and topological quantum devices.

Free-standing semiconductor nanowires constitute an ideal material system for the direct manipulation of electrical and optical properties by strain engineering. In this study, we present a direct quantitative correlation between electrical conductivity and nanoscale lattice strain of individual InAs nanowires passivated with a thin epitaxial In 0.6 Ga 0.4 As shell. With an in situ electron microscopy electromechanical testing technique, we show that the piezoresistive response of the nanowires is greatly enhanced compared to bulk InAs, and that uniaxial elastic strain leads to increased conductivity, which can be explained by a strain-induced reduction in the band gap. In addition, we observe inhomogeneity in strain distribution, which could have a reverse effect on the conductivity by increasing the scattering of charge carriers. These results provide a direct correlation of nanoscale mechanical strain and electrical transport properties in free-standing nanostructures.

Due to the ability to manipulate photons at nanoscale, plasmonics has become one of the most important branches in nanophotonics. The prerequisites for the technological application of plasmons include high confining ability (λ 0 /λ p ), low damping, and easy tunability. However, plasmons in typical plasmonic materials, i.e., noble metals, cannot satisfy these three requirements simultaneously and cause a disconnection to modern electronics. Here, the indium arsenide (InAs) nanowire is identified as a material that satisfies all the three prerequisites, providing a natural analogy with modern electronics. The dispersion relation of InAs plasmons is determined using the nanoinfrared imaging technique, and show that their associated wavelengths and damping ratio can be tuned by altering the nanowire diameter and dielectric environment. The InAs plasmons possess advantages such as high confining ability, low loss, and ease of fabrication. The observation of InAs plasmons could enable novel plasmonic circuits for future subwavelength applications., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Negative photoconductivity (NPC) and positive photoconductivity (PPC) are observed in the same individual InAs nanowires grown by metal-organic chemical vapor deposition. NPC displays under weak light illumination due to photoexcitation scattering centers charged with hot carrier in the native oxide layer. PPC is observed under high light intensity. Through removing the native oxide layer and passivating the nanowire with HfO 2 , we eliminate the NPC effect and realize intrinsic photoelectric response in InAs nanowire.

We determine the detailed differences in geometry and band structure between wurtzite (Wz) and zinc blende (Zb) InAs nanowire (NW) surfaces using scanning tunneling microscopy/spectroscopy and photoemission electron microscopy. By establishing unreconstructed and defect-free surface facets for both Wz and Zb, we can reliably measure differences between valence and conduction band edges, the local vacuum levels, and geometric relaxations to the few-millielectronvolt and few-picometer levels, respectively. Surface and bulk density functional theory calculations agree well with the experimental findings and are used to interpret the results, allowing us to obtain information on both surface and bulk electronic structure. We can thus exclude several previously proposed explanations for the observed differences in conductivity of Wz-Zb NW devices. Instead, fundamental structural differences at the atomic scale and nanoscale that we observed between NW surface facets can explain the device behavior.

We report on the fabrication and characterization of symmetric nanowire-based Josephson junctions, that is, Al- and Nb-based junctions, and asymmetric junctions employing superconducting Al and Nb. In the symmetric junctions, a clear and pronounced Josephson supercurrent is observed. These samples also show clear signatures of subharmonic gap structures. At zero magnetic field, a Josephson coupling is found for the asymmetric Al/InAs-nanowire/Nb junctions as well. By applying a magnetic field above the critical field of Al or by raising the temperature above the critical temperature of Al the junction can be switched to an effective single-interface superconductor/nanowire structure. In this regime, a pronounced zero-bias conductance peak due to reflectionless tunneling has been observed.